Fiber to The Home (FTTH) is the technical trend which has been continually pursued by people for the past twenty years but has not been popularized and developed on a large scale due to obstacles such as cost, technology, and requirements. In recent years, due to the development of PON technologies, only a simple optical branching device, as opposed to a node device, is required to be mounted at an optical branching point, allowing the FTTH network to become a research focus once more and potentially enter a rapid development stage. It is believed that, along with continuous emergence of new devices and new network construction plans, the FTTH network will be further developed in the coming years.
An optical access network (OAN), also referred to as FTTx network, with Fiber in the loop (FITL) as its formal name, provides various service interfaces to realize the positions of optical network units (ONUs) in the OAN for user integrated access. The OAN includes FTTH, Fiber to The Building (FTTB), Fiber to The Curb (FTTC), and the like. The FTTH is a final form of development of the OAN. Since the OAN has a high access bandwidth, the OAN can be used to provide a Triple Play service (transmitting voice, data, and video over one network line), thereby improving the user experience.
The OAN is mainly implemented by using the PON technologies. There are two mature PON technologies in the prior art. One is an Ethernet Passive Optical Network (EPON) technology that was proposed in 2001. In this technology, a system uses an Ethernet protocol, adopts a rate of 1.25 Gbit/s for uplink and downlink transmission, and can support Internet Protocol (IP) services with a high efficiency. That is, for the IP services, link layers between an optical line terminal (OLT) and the ONU adopt the Ethernet technology to communicate with each other through time-slot mapping and encapsulation, and an uplink and downlink symmetrical rate of 1.25 Gbit/s can be achieved. The other technology is a Gigabit Passive Optical Network (GPON) standard defined by the International Telecommunications Union (ITU) in January of 2003. Compared with the EPON, the GPON is more concerned with the capability of supporting multiple services such as time division multiplexing (TDM) and IP, a downlink rate of up to 2.5 Gbit/s, and the ability for uplink and downlink transmissions to adopt asymmetrical rates.
FIG. 1 is a schematic view of an architecture of the FTTx network in the prior art. As shown in FIG. 1, a home network, an OAN, and a service node function (SNF) are included.
An interface between the home network and the OAN is a user network interface (UNI), and an interface between the OAN and the SNF is a service node interface (SNI). The OAN mainly implements the access of the home network to a core network (CN) and is constituted by a series of transmission devices between the SNI and the UNI. For the FTTH, an optical network terminal (ONT) is connected to the OLT through an optical fiber, and the OLT serves as a termination point of the OAN. The OLT is connected to the SNF to realize service aggregation and delivery. For the FTTC, a network terminal (NT) is connected to the ONU through a copper cable, and the ONU is connected to the OLT through an optical fiber. For the FTTB, the NT is connected to the ONU through a copper cable, and the ONU is connected to the OLT through an optical fiber. The FTTB and the FTTC are different in distances by which the NT is connected to the ONU through the copper cable.
FIG. 2 is a schematic view of a reference network architecture of the OAN in the prior art. As shown in FIG. 2, a customer premises network (CPN), an OAN, and an SNF are included.
The CPN mainly includes a customer premises equipment (CPE) adapted to be connected to an adaptation function (AF) through a UNI. T is a reference point of the UNI. The UNI may be a digital subscriber line (DSL).
The OAN includes an AF, an ONU/ONT, an optical distribution network (ODN), and an OLT.
The AF, as an optional device in the OAN, may be an independent entity and is mainly responsible for providing mutual conversion between the ONU/ONT interface and the UNI. The ONU/ONT and the AF have a reference point (a) therebetween. The AF is adapted to convert the packet format from the UNI format to an interface (such as an Ethernet Link) format of the reference point (a) that can be connected to the ONU/ONT. The AF may be built into the ONU, thus the reference point (a) is not required. The AF may also be placed behind the OLT to perform the mutual conversion between the OLT interface and the SNI.
The ONU/ONT is adapted to provide a user-side interface for the OAN, to be connected to the ODN, and to convert a packet into a format (such as EPON encapsulation or GPON generic framing encapsulation) that can be transmitted on the ODN.
The ODN is adapted to provide a transmission means for the OLT and the ONU/ONT and is constituted by a passive physical device, an optical fiber, and an optical splitter or coupler for realizing downlink and uplink transmission of optical services.
The OLT is adapted to provide network interfaces for the ODN, be connected to one or more ODNs, and convert a packet into a packet format of the SNI (for example, the Ethernet link) for accessing the SNF. V is a reference point of the SNI. The downlink service is from the OLT to the ODN and then to the ONU, and the uplink service is from the ONU to the OLT. In the downlink direction, the OLT sends an Ethernet frame to each ONU through N ODNs (N is generally 4-64), and the downlink transmission method is similar to a shared medium network. In the uplink direction, services sent by a plurality of ONUs are received through the ODN and aggregated.
The SNF is adapted to interact with the OLT through an ETH-based aggregation network.
FIG. 3 is a schematic view of an architecture of an ETH-based aggregation network in the prior art. As shown in FIG. 3, the OLT is an ETH-based aggregation node device, and an ETH-based aggregation network exists between the OLT and an IP network edge node device such as a broadband network gateway/broadband remote access server (BNG/BRAS). The OLT interacts with an IP network through the ETH-based aggregation network. The IP network edge node device is one part of the SNF. In addition, an access node (AN) such as a DSL access multiplexer (DSLAM) and the ONU/ONT can form a PON-fed AN. In FIG. 3, the PON-fed AN is a PON-fed DSLAM.
In the prior art, since the PON technology is connection-oriented and the ETH technology is connectionless, the connection-oriented PON-based network and the connectionless ETH-based aggregation network have poor coordination. Furthermore, the ETH-based aggregation network does not have strict quality of service (QoS) mechanism and operation, administration and maintenance (OAM) mechanism, and thus cannot support some services, especially the TDM or session-based services. In order to solve this problem, various ETH-based aggregation networks simulating connection characteristics are adopted in the prior art.
For example, at present, an ETH-based aggregation network based on a Provider Backbone Transport (PBT) technology is proposed for connection simulation. Connection management and configuration functions for the PBT network are newly added, and medium access control (MAC) address learning and spanning tree protocol as well as broadcast and multicast functions of unknown packets are disabled in PBT virtual local area network (VLAN). However, the Ethernet loses some original excellent properties, and the user experience is degraded at the same time. Furthermore, due to the technical enhancement, the complexity of the ETH variant is greatly increased, which does not conform to the properties of the ETH.
Further, at present, a multi-protocol label switching (MPLS)-based aggregation network is also proposed to support connection. However, another problem arises in that the MPLS does not support the multicasting function and so the user experience is degraded.
Moreover, the ETH-based aggregation network is an active network and must be rented to build equipment rooms, and battery cells and uninterrupted power systems (UPSs) must be configured for all aggregation network node devices between the OLT and the IP network edge node, resulting in high network construction and operation costs.